Oled lighting devices having multi element light extraction and luminescence conversion layer

ABSTRACT

An apparatus such as a light source has a multi element light extraction and luminescence conversion layer disposed over a transparent layer of the light source and on the exterior of said light source. The multi-element light extraction and luminescence conversion layer includes a plurality of light extraction elements and a plurality of luminescence conversion elements. The light extraction elements diffuses the light from the light source while luminescence conversion elements absorbs a first spectrum of light from said light source and emits a second spectrum of light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation and claims the benefit of priorityunder 35 U.S.C. Section 120 of U.S. application Ser. No. 11/345,795,filed Feb. 1, 2006, which is a continuation-in-part of U.S. applicationSer. No. 11/264,516, filed Oct. 31, 2005.

This application is also related to currently co-pending and commonlyassigned U.S. application Ser. No. 11/215,548, filed on Aug. 29, 2005.The disclosure of each prior application is considered part of and isincorporated by reference in the disclosure of this application.

GOVERNMENT RIGHTS

This invention was made with Government support under Contract No.DE-FC26-04NT41947 awarded by the Department of Energy. The Governmentmay have certain rights in the invention.

BACKGROUND

Display and lighting systems based on LEDs (Light Emitting Diodes) havea variety of applications. Such display and lighting systems aredesigned by arranging a plurality of photo-electronic elements(“elements”) such as rows of individual LEDs. LEDs that are based uponsemiconductor technology have traditionally used inorganic materials,but recently, the organic LED (“OLED”) has become a potentialsubstitute. Examples of other elements/devices using organic materialsinclude organic solar cells, organic transistors, organic detectors, andorganic lasers.

An OLED is typically comprised of two or more thin organic layers (e.g.,an electrically conducting organic layer and an emissive organic layerwhich emits light) which separate an anode and a cathode layer. Under anapplied forward potential, the anode injects holes into the stack oforganic layers, while the cathode injects electrons. The injected holesand electrons each migrate (under the influence of an externally appliedelectric field) toward the opposite electrode and recombine in theemissive layer under emission of a photon. Similar device structure anddevice operation applies for OLEDs consisting of small molecule organiclayers and/or polymeric organic layers. Each of the OLEDs can be a pixelelement in a passive/active matrix OLED display or an single elementused as a general area light source and the like.

The construction of OLED light sources and OLED displays from individualOLED elements or devices is well known in the art. The displays andlight sources may have one or more common layers such as commonsubstrates, anodes or cathodes and one or more common organic layerssandwiched in between. They may also consist of photo-resist orelectrical separators, bus lines, charge transport and/or chargeinjection layers, and the like. Typically, a transparent orsemi-transparent glass substrate is used in bottom-emitting OLEDdevices.

White-emitting OLED-lighting devices can be generated by applying acontinuous down-conversion layer on the light emitting side of a blueOLED. The down-conversion layer comprises of a color changing material,for example phosphor particles or organic dyes.

The phosphor layer can be structured as illustrated in thecommonly-assigned US patent application entitled “StructuredLuminescence Conversion Layer” filed on Oct. 31, 2005, bearing Ser. No.11/264,516, and published as U.S. Publication No. 20070096634. Suchstructuring gives more flexibility in designing output spectra ofdown-conversion light sources. This flexibility allows finding a bettercompromise between efficiency and color rendering.

The mismatch of the refractive index between air and the OLED leads tomost of the generated light being lost through total internal reflectioninto wave guiding modes and self absorption. Applying a phosphor layeror a scattering layer on the light emitting side of an OLED-deviceincreases the output of OLEDs due to volumetric scattering mechanisms.Light extraction can also be improved by texturing the light emittingside of an OLED, for example by sand blasting or etching as described ina currently co pending commonly assigned US patent application entitled“Using Prismatic Microstructured Films for Image Blending in OLEDs”filed on Aug. 29, 2005, bearing Ser. No. 11/215,548 and published asU.S. Publication No. 20070046161.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of an embodiment of anelectroluminescent (EL) apparatus 200 according to at least oneembodiment of the invention.

FIG. 2 shows a cross-sectional view of exemplary EL apparatus inaccordance with at least one embodiment of the invention.

FIGS. 3A-3B illustrates exemplary patterns for multi element lightextraction and luminescence conversion layers from a top view.

DETAILED DESCRIPTION

In at least one embodiment of the invention, an electroluminescent (EL)apparatus is disclosed which utilizes 1) an OLED device or light sourceincluding a transparent layer for light emission; and 2) a multi-elementlight extraction and luminescence conversion layer disposed in the pathof light emission from the OLED device or light source and on theoutside of the OLED device on the exterior side of the transparentlayer. The multi-element light extraction and luminescence conversionlayer comprises at least one light extraction element(s) and at leastone luminescence conversion element(s). The light extraction element(s)diffuses the light from the light source while the luminescenceconversion element(s) absorbs part of a first spectrum of light from thelight source and emits a second spectrum of light. The non-absorbed partof the first spectrum of light and the second spectrum of light from theluminescence conversion element(s) combines with the diffused lightoutput from the light extraction element(s) to give a total outputspectrum of light for the electroluminescent apparatus. The elements ofthe layer adjacent to one another and adjacent directly to saidtransparent layer. Thus, they are not stacked vertically, but rathereach element occupies a certain area on the exterior surface of thetransparent layer of the light source.

The luminescence conversion element(s) comprises at least one colorchanging material(s) (such as a phosphor) which is defined herein as amaterial which can absorb light in one spectrum and emit light inanother spectrum. The color-changing material(s) within thecolor-changing regions may be embedded in a transparent matrix. All ofthe color-changing material(s) in the luminescence conversion elementcan be of the same material or can be different material and maycomprise for instance of scattering particles, phosphor particles and soon. For instance, some of the luminescence conversion element(s) may beorange emitting while others are yellow emitting. The ratio of thesurface area (or width or other dimension) of the luminescenceconversion element(s) versus the light extraction element(s) affects thetotal output spectrum of the EL apparatus. Due to the addition of thisratio, the use of a multi-element light extraction and luminescenceconversion layer gives greater flexibility in designing the outputspectra than when uniform conversions layers are used. The flexibilityenables finding a better compromise between efficiency and colorrendering.

According to a model described in literature, the output spectrum of anEL apparatus with a uniform down conversion or color-changing materiallayer is given by:

A _(a,δ)(λ)=S ₀(λ)exp[−α₁(λ)δ]+W _(a,δ) C _(a,δ)(λ)P(λ)  (1),

where α(λ) is the absorption coefficient of the luminescence conversionelement as related to the color-changing material concentration, δ isthe effective optical path length which may be related but notnecessarily equal to the thickness of the element (due to scattering).P(λ) is normalized so that its integral over all wavelength is unity.W_(a,δ) is a weight factor. C is the self absorption correction. S₀(λ)is the emission spectrum of the light source.

Based on the rules of color mixing, the output spectrum of an identicalEL apparatus with a multi-element light extraction and luminescenceconversion layer in accordance with the invention is given by:

B _(α,δ,x)(λ)=(1−x)S ₀(λ)+x[S ₀(λ)exp[−α(λ)δ]+W _(a,δ) C_(a,δ)(λ)P(λ)]  (2),

where x(=0 . . . 1) is related to the size/configuration of theluminescence conversion elements, and (1−x) is related to thesize/configuration of the light extraction elements.

The weight factor W_(a,δ) is given by:

W _(a,δ) =Q∫S ₀(λ)(1−exp[−α(λ)])dλ,

where Q is the quantum yield of the color-changing material used in theluminescence conversion elements.

The self absorption correction C_(α,δ,x)(λ) is given by:

Cα,δ,x(λ)=exp[−α(λ)δ]/(1−Q∫P(λ)(1−exp[−α(1)δ])dλ).

The above assumes effective path length for the absorption process isequal to the effective path length for the luminescence. As a result ofthe model described in equation 2 above, the differentiation betweenluminescence conversion elements (related to the multiplier x) and lightextraction elements (related to the multiplier 1−x) enables a greaterability to tune the output spectra more precisely.

Preferably, the color-changing material(s) selected for inclusion in theluminescence conversion element(s) are such that the light output of theEL apparatus is below the photon saturation limit of the luminescenceconversion element. In alternate embodiments, the photon saturationlimit may even be exceeded.

The light extraction element(s) of the multi-element light extractionand luminescence conversion layer includes a plurality ofnon-color-changing light transmitting regions. The light extractionelement has a refractive index (n₁) equal or close to the refractiveindex of the transparent layer of the OLED device or light source (whichis adjacent to and transmits light to the multi-element layer). Therefractive index (n₂) of the luminescence conversion element is designedto be less than n₁. The preferred shape of the light extraction elementis trapezoidal or an emboss-type geometry. The preferred shape of theluminescence conversion element is flat or lens-like. Preferably, boththe light extraction element(s) and the luminescence conversionelement(s) comprise of materials with a low absorption coefficient.

The light extraction element can be fabricated by molding an uncuredcontinuous layer or by photolithography. The luminescence conversionelement can be fabricated by volume casting, screen printing, inkjetprinting, photolithography, and so on.

FIG. 1 shows a cross-sectional view of an embodiment of anelectroluminescent (EL) apparatus 200 according to at least oneembodiment of the invention. The EL apparatus 200 includes an OLEDdevice 205 and a multi-element light extraction and luminescenceconversion layer (MLELC) layer 230. OLED device 205 includes substrate208 and a first electrode 211 on the substrate 208. The first electrode211 may be patterned for pixilated applications or un-patterned forbacklight or other general lighting applications. The OLED device 205also includes a semiconductor stack 214 on the first electrode 211. Thesemiconductor stack 214 includes at least the following: (1) an anodebuffer layer (ABL) 215 and (2) an active light emitting layer (EML) 216.

As shown in FIG. 1, the OLED device 205 is a bottom-emitting device. Asa bottom-emitting device, the first electrode 211 acts as an anode, andthe ABL 215 is deposited onto the first electrode 211, and the EML 216is deposited onto the ABL 215. Finally, the OLED device 205 alsoincludes a second electrode 217 deposited onto the organic semiconductorstack 214. Other layers than that shown in FIG. 1 may also be added suchas insulating layers, barrier layers, electron/hole injection andblocking layers, getter layers, and so on. In accordance with theinvention, the MLELC layer 230 is disposed on the outside of the OLEDdevice 205. More specifically, in the configuration shown, the MLELClayer 230 is disposed on the substrate 208. The OLED device 205 and theMLELC layer 230 together comprise the EL apparatus 200. Exemplaryembodiments of these layers are described in greater detail below.

Substrate 208:

The substrate 208 can be any material, which can support the additionallayers and electrodes, and is transparent or semi-transparent to thewavelength of light emitted by the OLED device 205. Preferable substratematerials include glass, quartz, and plastic, preferably, thin, flexibleglass. The preferred thickness of the substrate 208 depends on thematerial used and on the application of the device. The substrate 208can be in the form of a sheet or continuous film. The continuous film isused, for example, for roll-to-roll manufacturing processes which areparticularly suited for plastic, metal, and metallized plastic foils.

First Electrode 211:

In the bottom-emitting configuration, the first electrode 211 functionsas an anode (the anode is a conductive layer which serves as ahole-injecting layer). Typical anode materials include metals (such asplatinum, gold, palladium, indium, and the like); conductive oxides(such as lead oxide, tin oxide, indium-tin oxide (ITO), and the like);graphite; and doped conducting polymers (such as polyaniline,polypyrrole, polythiophene, and the like). Preferably, the firstelectrode 211 is comprised of indium-tin oxide (ITO).

For OLEDs, the first electrode layer 211 is usually thin enough so as tobe semi-transparent and allow at least a fraction of light to transmitthrough (in bottom emitting OLEDs). The thickness of the first electrode211 is from about 10 nm to about 1000 nm, preferably, from about 50 nmto about 200 nm, and more preferably, is about 100 nm. As such, anythin-film deposition method may be used in the first electrodefabrication step. These include, but are not limited to, vacuumevaporation, sputtering, electron beam deposition, chemical vapordeposition, etching and other techniques known in the art andcombinations thereof. The process also usually involves a baking orannealing step in a controlled atmosphere to optimize the conductivityand optical transmission of anode layer. Photolithography can then beused to define any pattern, if desired, upon the first electrode 211.

ABL 215:

The ABL 215 has good hole conducting properties and is used toeffectively inject holes from the first electrode 211 to the EML 216.The ABL 215 is made of polymers or small molecule materials or othermaterial. For example, the ABL 215 can be made from tertiary amine orcarbazole derivatives both in their small molecule or their polymerform, conducting polyaniline (“PANI”), or PEDOT:PSS (a solution ofpoly(3,4-ethylenedioxythiophene) (“PEDOT”) and polystyrenesulfonic acid(“PSS”) (available as Baytron P from HC Starck). The ABL 215 can have athickness from about 5 nm to about 1000 nm, and is conventionally usedfrom about 50 to about 250 nm. Other examples of the ABL 215 includecopper phthalocyanine (CuPc) films with preferred thicknesses between 10and 50 nm. Other such examples of ABL materials are well-known in theart and can readily be substituted for or combined with theabove-mentioned materials.

The ABL 215 can be formed using selective deposition techniques ornonselective deposition techniques. Examples of selective depositiontechniques include, for example, ink jet printing, flex printing, andscreen printing. Examples of nonselective deposition techniques include,for example, spin coating, dip coating, web coating, and spray coating.

EML 216:

The active light emitting layer (EML) 216 is comprised of an organicelectroluminescent material which emits light upon application of apotential across first electrode 211 and second electrode 217. The EMLmay be fabricated from materials organic or organo-metallic in nature,and may include polymer, monomer and/or small molecule emitters. As usedherein, the term organic also includes organo-metallic materials.Light-emission in these materials may be generated as a result offluorescence and/or phosphorescence.

Organic materials may comprise of one or more of a polymer, polymerblend, monomer, oligomer, co-polymer, an organic side-group, smallmolecule or blend of any of these. The EML 216 can comprise of, forexample, conjugated EL polymers, such as polyfluorenes, polythiophenes,polyphenylenes, polythiophenevinylenes, polyspiro polymers, orpoly-p-phenylenevinylenes or their families, copolymers, derivatives,blends, or mixtures thereof that emit white, red, blue, yellow, orange,green or any single or combined spectrum of light.

The EML 216 can be a continuous film that is non-selectively deposited(e.g. spin-coating, dip coating etc.) or discontinuous regions that areselectively deposited (e.g. by ink-jet printing). EML 216 may also befabricated by vapor deposition, sputtering, vacuum deposition etc. asdesired.

The EML 216 can be composed of more than one light emitting element (forinstance, a host and dopant). In the case of two light-emittingelements, the relative concentration of the host element and the dopantelement can be adjusted to obtain the desired color. The EML 216 canemit light in any desired color and be comprised of polymers,co-polymers, dopants, quenchers, and hole and electron transportmaterials as desired. For instance, the EML 216 can emit light in blue,red, green, orange, yellow or any desired combination of these colorsand in some applications, may include a combination of emitting elementswhich produce white light. The EML 216 may also comprise a plurality ofseparate emissive sub-layers.

In addition to active electroluminescent materials that emit light, EML216 can also include materials capable of charge transport. Chargetransport materials include polymers or small molecules that cantransport charge carriers. For example, organic materials such aspolythiophene, derivatized polythiophene, oligomeric polythiophene,derivatized oligomeric polythiophene, pentacene, triphenylamine, andtriphenyldiamine.

Second Electrode 217:

In the bottom-emitting configuration, the second electrode 217 functionsas the cathode (i.e. as the conductive layer which serves as anelectron-injecting layer and which is comprised of a material with a lowwork function). While many materials, which can function as a cathode,are known to those of skill in the art, most preferably a compositionthat includes aluminum, indium, silver, gold, magnesium, calcium,lithium, lithium fluoride, cesium fluoride, sodium fluoride, and barium,or combinations thereof, or alloys thereof, is utilized. Aluminum, andcombinations of calcium and aluminum, barium and aluminum, lithiumfluoride and aluminum, lithium fluoride with calcium and aluminum,magnesium and silver or their alloys are especially preferred.

Preferably, the thickness of second electrode 423 is from about 10 nm toabout 1000 run, more preferably from about 50 nm to about 500 nm, andmost preferably from about 100 nm to about 300 nm. While many methodsare known to those of ordinary skill in the art by which the firstelectrode material may be deposited, vacuum deposition methods, such asthermal vacuum evaporation, sputtering or electron-beam deposition arepreferred. Other layers (not shown) such as a barrier layer and getterlayer may also be used to protect the electronic device. Such layers arewell-known in the art and are not specifically discussed herein.

Multi-element light extraction and luminescence conversion layer (MLELC)230 OLED device 205 as shown is a bottom-emitting OLED, and thus, thelight emitted from the EML 217 passes through the substrate 208. Inaccordance with various embodiments of the invention, a multi-elementlight extraction and luminescence conversion (MLELC) layer 230 isdisposed on the exposed external side of the substrate 208 (and thus, onthe exterior of the OLED device 205) to modify and tune the light outputfrom EL apparatus 200. In at least one embodiment of the invention, theMLCLE 230 is comprised of at least one light extraction element(s) 230Aand at least one luminescence conversion element(s) 230B.

The luminescence conversion element(s) 230B will comprise of afluorescent or phosphorescent material or any color changing materialwhich can absorb light in one spectrum and emit light in anotherspectrum. The color-changing materials within the luminescenceconversion element(s) 230B may be embedded in a transparent matrix. Allof the luminescence conversion element(s) 230B can be of the samematerial or can be different material. For instance, some of theluminescence conversion element(s) 230B may be orange emitting whileanother portion is yellow emitting. Exemplary color-changing materialswhich could be used in forming the luminescence conversion element(s)230B include, but are not limited to, scattering particles, organic andinorganic dyes, cerium doped garnets, nitride phosphors, ionic phosphorslike SrGa₂S₄:Eu²⁺ or SrS:Eu²⁺, quantum dots, fluorescent dyes orconjugated polymers. The color-changing materials in each case can bedissolved or blended into transparent matrix materials such as silicone,epoxy, adhesives, polymethylmethacrylate, polycarbonate and so on. Theshape/geometry of the luminescence conversion element(s) 230B can beflat or lens-like, or any desirable shape. The light extractionelement(s) 230A comprise materials that have a refractive index roughlyequal to the transparent layer of the OLED or light source to which itis attached. In the embodiment shown in FIG. 1, light extractionelement(s) 230A would have a refractive index that matches therefractive index of substrate 208 of OLED device 205. The lightextraction element(s) 230A would also have a refractive index greaterthan or equal to the refractive index of the luminescence conversionelements 230B. In one embodiment of the invention, the light extractionelement(s) 230A would have no color-changing materials, and in alternateembodiments, may include color-changing materials. The shape/geometry ofthe light extraction element(s) 230A is trapezoidal or emboss in nature.The angles of the geometry for light extraction element(s) 230A will bedesigned so as to enhance outcoupling of light. Preferably, both thelight extraction element(s) and the luminescence conversion element(s)comprise of materials with a low absorption coefficient.

The ratio of the surface area (or width or other dimension) of theluminescence conversion element(s) 230A versus the light extractionelement(s) 230B affects the total output spectrum of the EL apparatus.Due to the addition of this ratio, the use of a multi-element lightextraction and luminescence conversion layer gives greater flexibilityin designing the output spectra than when uniform conversions layers areused. The flexibility enables finding a better compromise betweenefficiency and color rendering.

The thickness of the MLELC layer 230 varies as among the lightextraction element(s) 230A and the luminescence conversion elements230B. It depends on the desired output spectrum of the device and theconcentration of the CCM (color-changing material) in the luminescenceconversion element(s) 230B. The concentration of the CCM may be limitedby quenching and aggregation effects. Furthermore, scattering effectsare dependent on the concentration of the CCM. In some embodiments, theMLELC layer 230 can be attached to the substrate 208 using an opticallyadhesive glue, which may additionally also be curable by ultravioletradiation, or an index matching gel. In other embodiments, the MLELClayer 230 can be deposited or formed directly on substrate 208 by screenprinting, inkjet printing or other selective deposition techniques ormasking combined with non-selective deposition techniques. Further, theMLELC layer 230 can utilize a cross-linkable material which can then bechemically bonded to the substrate 208. More specifically, the lightextraction element(s) 230A can be formed by molding an uncured layer(s),by a lithography process, or by other physical/chemical application orattachment. The luminescence conversion element(s) 230B can befabricated by selective deposition techniques such as volume casting,inkjet printing, screen printing, shadow masking and so on.

FIG. 2 shows a cross-sectional view of exemplary EL apparatus inaccordance with at least one embodiment of the invention. EL apparatus308 comprises a light source 305 and a multi-element light extractionand luminescence conversion (MLELC) layer 330 similar to MLELC layer 230of FIG. 1. Layer 330 has at least one light extraction element(s) 330Aand at least one luminescence conversion element(s) 330B. The width ofthe individual light extraction element(s) at the interface to the lightsource 305 is “a” while the width of the individual luminescenceconversion element(s) at the interface to the light source 305 is “b”.The ratio between “a” and “b” can be used to determine the outputspectrum as described in equation 2 above (where “b” is 1−x and “a” isx). As shown, the physical thickness is uniform over the structuredluminescence conversion layer 330, however, in other embodiments, thethickness may be varied from one luminescence conversion element toanother or varied within even a given luminescence conversion elementand may likewise vary as among the light extraction elements. Theluminescence conversion element(s) 330B absorb a first spectrum of lightemitted from light source 305 and emit a second spectrum of light. Thelight extraction element(s) 330A pass through the light emitted fromlight source 305 without spectral color shift (no specific or littleintended color change) but with enhanced output. For instance, the lightextraction element(s) 330A may comprise an optical adhesive or glass orsimilar light transmissive material. The shape, function and compositionof the light extraction element(s) 330A and luminescence conversionelements 330B are similar to that described for light extractionelement(s) 230A and luminescence conversion elements 230B of FIG. 1. Thetotal light output and spectrum is a combination of the non-absorbedfirst spectrum of light, the emitted second spectrum of light and theeffect of the light extraction due to the light extraction elements330A.

FIGS. 3A-3B illustrates exemplary patterns for multi-element lightextraction and luminescence conversion layers from a top view. FIG. 3Ashows a checkered pattern for a multi-element light extraction andluminescence conversion layer 430 where light extraction elements 430Aand luminescence conversion elements 430B alternate insquares/rectangles across the top. FIG. 3B shows a striped pattern forthe multi-element light extraction and luminescence conversion layer431. The luminescence conversion elements 431A are shaded while thelight extraction elements 431B are in an emboss shape or trapezoidal.This pattern would correspond, for instance, to the cross-sectional viewof the multi-element light extraction and luminescence conversion layer330 shown in FIG. 2. Other alternate patterns not shown include a meshpattern where the light extraction elements and luminescence conversionelements are stripes which overlap one another. Yet other patterns notshown include a circular pattern for the color-changing regions. Oneexample of this pattern would be cut conical shapes for light extractionelements surrounded by color changing materials which comprise theluminescence conversion element(s). The patterns shown in FIGS. 3A-3Bare merely exemplary of the possible patterns for multi-element lightextraction and luminescence conversion layers and are not intended to belimiting or exhaustive. Though shown in repeating patterns, themulti-element light extraction and luminescence conversion layer mayalso have random or non-repeating or partially repeating lightextraction and luminescence conversion elements. Furthermore, asmentioned above the thicknesses of luminescence conversion elements orlight extraction elements may not be uniform and as compared to oneanother may vary.

Top Emitting OLED Devices

In an alternative configuration to that shown in FIG. 1 and describedabove, the first electrode 211 functions as a cathode (the cathode is aconductive layer which serves as an electron-injecting layer and whichcomprises a material with a low work function). The cathode, rather thanthe anode, is deposited on the substrate 208 in the case of atop-emitting OLED. In this alternative configuration, the secondelectrode layer 217 functions as an anode (the anode is a conductivelayer which serves as a hole-injecting layer and which comprises amaterial with work function greater than about 4.5 eV). The anode,rather than the cathode, is deposited on the semiconductor stack 214 inthe case of a top-emitting OLED.

In embodiments where the OLED is “top-emitting” as discussed above, theanode may be made transparent or translucent to allow light to pass fromthe semiconductor stack 214 through the top of the device. In suchcases, the multi-element light extraction and luminescence conversionlayer would be attached, bonded or cured to the anode 217 (or to a glassor other material which encapsulates and protects the anode) rather thanto the substrate 208 as with a bottom-emitting OLED shown in FIG. 1.

The OLED lighting sources and displays produced from a combination orarrays of EL devices described earlier can be used within applicationssuch as information displays, general, industrial and area lighting,telephones, printers, computer displays, televisions, and illuminatedsigns.

As any person of ordinary skill in the art of light-emitting devicefabrication will recognize from the description, figures, and examplesthat modifications and changes can be made to the embodiments of theinvention without departing from the scope of the invention defined bythe following claims.

1. An electroluminescent apparatus, comprising: a light sourcecomprising a transparent layer capable of at least partiallytransmitting light out from said light source; and a multi-element lightextraction and luminescence conversion layer disposed over saidtransparent layer and on the exterior of said light source, saidmulti-element light extraction and luminescence conversion layercomprising a plurality of light extraction elements and a plurality ofluminescence conversion elements, wherein: said light extractionelements diffuse said light from said light source, said luminescenceconversion elements absorb a first spectrum of light from said lightsource and emit a second spectrum of light, said non absorbed firstspectrum of light, said second spectrum of light and said diffused lightoutput due to said light extraction elements form a total outputspectrum of light for said electroluminescent apparatus, said lightextraction elements and luminescence conversion elements are adjacent toone another and directly adjacent to said transparent layer, and theplurality of luminescence conversion elements and plurality of lightextraction elements are arranged in an alternating pattern, a meshedpattern or such that the plurality of luminescence conversion elementsare conically sectioned.
 2. The apparatus of claim 1 wherein said lightextraction elements have a refractive index matching the refractiveindex of the transparent layer.
 3. The apparatus of claim 1 wherein saidlight extraction elements have a refractive index greater than therefractive index of the luminescence conversion elements.
 4. Theapparatus of claim 1 wherein said luminescence conversion elementscomprise at least one color changing material.
 5. The apparatus of claim4 wherein said color changing material is a fluorescent orphosphorescent dye.
 6. The apparatus of claim 4 wherein said colorchanging material is in a transparent matrix material.
 7. The apparatusof claim 6 wherein said transparent matrix material is at least one ofsilicone, epoxy, polymethylmethacrylate or polycarbonate.
 8. Theapparatus of claim 1 wherein said multi-element layer is attachedphysically and/or chemically to said transparent layer.
 9. The apparatusof claim 1 wherein said light extraction elements have a trapezoidalgeometry.
 10. The apparatus of claim 1 wherein said device is part of alight source application.
 11. The apparatus of claim 1 wherein saidlight source is an OLED device.
 12. The apparatus of claim 1 whereinsaid transparent layer is an electrode or an encapsulation layer andtransmits light out of said apparatus.
 13. The apparatus of claim 1wherein said transparent layer is a substrate.
 14. The apparatus ofclaim 1 wherein said light extraction elements comprise a non-absorbing,light transmissive material.
 15. The apparatus of claim 1 wherein saidluminescence conversion elements comprise at least one of an organicfluorescent dye, perylene, coumarin, fluorescent conjugated polymer,organic phosphorescent dye, conjugated phosphorescent polymer, inorganiccolor changing material, cerium doped garnet, nitride phosphor, ionicphosphor, or quantum dot.
 16. The apparatus of claim 1 wherein saidluminescence conversion elements have a lens-like or flat geometry. 17.The apparatus of claim 1 wherein said luminescence conversion elementsand said light extraction elements comprise a material with a lowabsorption coefficient.
 18. The apparatus of claim 1 wherein saidplurality of light extraction elements and plurality of luminescenceconversion elements are arranged in an alternating pattern.
 19. Theapparatus of claim 1 wherein said plurality of light extraction elementsand plurality of luminescence conversion elements are arranged in astriped pattern.
 20. The apparatus of claim 1 wherein said plurality oflight extraction elements and a plurality of luminescence conversionelements are arranged in a mesh pattern.
 21. The apparatus of claim 1wherein said plurality of light extraction elements and a plurality ofluminescence conversion elements are arranged such that said pluralityof luminescence conversion elements are conically sectioned.